1. Field of the Invention
The present invention relates to a thrust bearing device used in rotating machines and, more particularly, to a thrust bearing device to which a thrust load is applied when the rotational axis is stopping.
2. Prior Art
If a thrust load is applied, for example, when the rotational axis is stopping, a static pressure type of thrust bearing is used which forms an oil film between the sliding surface of the rotational axis side and the sliding surface of the bearing side by supplying a high-pressure lubricant, and uses the static pressure of the oil film to support the thrust load. A contact between the sliding surface of the rotational axis side and the sliding surface of the bearing side is thus avoided, preventing the bearing from being damaged. As an example of this static pressure type of thrust bearing, an arrangement has been disclosed in which oil supply openings (pockets) formed on a pad sliding surface and oil supply holes communicating with the oil supply openings are provided with a tilting pad thrust bearing (see Patent Document 1, for example).
For small rotary machines, for example, tilting pad thrust bearings having a complex structure and thereby including many parts result in high costs, so tapered land thrust bearings having a simple structure and thereby reducing the number of parts are often used. In general, a tapered land thrust bearing has a plurality of oil grooves formed on the sliding surface on the bearing side, which extend in radial directions and lead a lubricant, and also includes a plurality of tapered lands, which comprises tapered parts (tilted planes) and lands (planes) formed among the plurality of grooves. The lubricant is led to the tapered lands through the oil grooves when, for example, the rotational axis is rotating at high speed. A flow along the periphery of the tapered lands generates a dynamic pressure. The dynamic pressure supports the thrust load. The ratio of the area of the lands to the area of the tapered lands is preferably set to about 20% (see Non-patent Document 1, for example).
Patent Document 1: Japanese Patent Publication No. 2006-274244.
Non-patent Document 1: Japanese Society of Tribologists, Toraiboroji hando bukku (tribology handbook), Yokendo, 2001, p. 58